Do not open bug reports before troubleshooting is finished. A particular project might have 2 developers, 100 open bug reports, 1,000 active users on the forums and IRC, and a million users overall. You should troubleshoot the issue on your own first, as much as you can, and then rely on other users in the community for help, before interacting with the development team.

You’ve gathered enough information for the team to work on (error messages, steps to reproduce, etc.), and you’re confident it will quickly lead to a fix.

The issue hasn’t already been reported.

Important

Although developers can help with questions, troubleshooting and analysis, there are very few of them and many other bug reports open. Use them for what they’re best at: Fixing things. You should only open bug reports when everything is done already (observation, troubleshooting, analysis, gathering of information, understanding of the cause) and the only thing missing is the actual fix. Don’t rely on developers to do the analysis/troubleshooting for you. A bug you don’t understand is unlikely to be a bug they’ll fix overnight.